This investigation plans to study the pathogenesis of the lesions in experimental aspergillosis, particularly pulmonary aspergillosis. It is proposed to study in detail how agents or conditions such as corticosteroids, irradiation, cytotoxic drugs, transplantable leukemia and alloxan diabetes alter the susceptibility of mice to infection by exposure to viable spores of Aspergillus flavus. In in vivo and in vitro studies pulmonary and peritoneal macrophages will be exposed to non-germinating (resting) or germinating spores. The reactions and consequences of such exposures will be studied with biochemical, mycological, histochemical and electron microscopic techniques. These studies are designed to gain an understanding of the pathogenesis of this experimental infection at a cellular level.